The posterior root of the zygoma may be considered approximately the line of demarcation between the roof of the antrum and mastoid process, and the floor of the middle fossa of the skull. This, however, is only a rough guide, as in some cases, especially of the brachycephalic type, the middle fossa may dip below this point. If this ridge is not well marked, then Reid’s base-line must be taken as the guide.
Just behind the auditory meatus, at its upper posterior margin, is the spine of Henle, which forms the anterior boundary of the suprameatal triangle. Macewen, who first described this triangle, gave it as a guide for the exposure of the antrum. Experience, however, has shown that no reliance can be placed on this as a landmark, as, if the bone is chiselled through at this point, it is by no means uncommon to expose the dura mater of the middle fossa. A point 10 millimetres (two-fifths of an inch) behind the spine of Henle corresponds to the anterior border of the sigmoid sinus. Behind the suprameatal triangle and beneath the zygomatic ridge is the body of the mastoid process, which has a smooth surface and is perforated by small foramina through which pass tiny vessels.
The antrum, in the adult, is situated at a slightly higher level than the tympanic membrane, its floor roughly corresponding with a line drawn horizontally backwards through the middle of the posterior wall of the bony meatus.
HISTORY OF THE MASTOID OPERATION
Although opening of the mastoid process as an operative measure dates back to the eighteenth century, yet Schwartze, in 1873, was the first to establish the operation as a practical procedure.
Schwartze’s operation consisted in the simple opening of the antrum and mastoid cells, leaving the middle ear untouched. This procedure was carried out no matter whether the disease was recent or long standing. It soon became recognized, however, that this operation did not effect a cure in all cases, more especially in those in which the disease involved the walls of the tympanic cavity.
Küster, in 1889, suggested removal of the posterior wall of the external auditory meatus, and about the same time von Bergmann advocated removal of the outer attic-wall. The Küster-Bergmann operation, first practised by Zaufal, may therefore be considered to be the origin of the complete mastoid operation.
Stacke’s name is frequently though wrongly mentioned in association with the complete operation, which is sometimes termed the Schwartze-Stacke operation. Stacke’s operation was devised with a view to removal of the ossicles and outer wall of the attic in those cases in which the bone disease was limited to these regions. This operation, however, is occasionally of service in the performance of the complete mastoid operation (see [p. 397]).
Thus the year 1889 may be considered as the starting-point of the complete mastoid operation. Since that date many modifications have been introduced, the majority of which are not worthy of reference.
After the technique of the operation had been developed and practised for some time, more careful attention was directed to the after-treatment. In the earlier days of the radical operation it was the rule to leave the wound open and to plug it with gauze, or to insert a drainage tube which was carried through the membranous portion of the external meatus.